The Liquid Crystal Display (LCD) possesses advantages of thin body, power saving and no radiation to be widely used in many application scope. Such as LCD TV, mobile phone, personal digital assistant (PDA), digital camera, notebook, laptop, and dominates the flat panel display field.
Most of the liquid crystal displays on the present market are backlight type liquid crystal displays, which comprise a liquid crystal display panel and a backlight module. The working principle of the liquid crystal display panel is that the Liquid Crystal is injected between the Thin Film Transistor Array Substrate (TFT array substrate) and the Color Filter (CF). The light of backlight module is refracted to generate images by applying driving voltages to the two substrates for controlling the rotations of the liquid crystal molecules.
In the active liquid crystal display, each pixel is electrically coupled to a thin film transistor (TFT), and the gate thereof is coupled to a level scan line, and the drain is coupled to a vertical data line, and the source is coupled to the pixel electrode. The enough voltage is applied to the level scan line, and all the TFTs electrically coupled to the scan line are activated. Thus, the signal voltage on the data line can be written into the pixel to control the transmittances of different liquid crystals to achieve the effect of controlling colors. The driving of the level scan line in the present active liquid crystal display is mainly accomplished by the external Integrated Circuit (IC). The external IC can control the charge and discharge stage by stage of the level scan lines of respective stages. The GOA (Gate Driver on Array) technology, i.e. the array substrate row driving technology can utilize the array manufacture process of the liquid crystal display panel to manufacture the gate driving circuit on the TFT array substrate for realizing the driving way of scanning the gates row by row. The GOA technology can reduce the bonding procedure of the external IC and has potential to raise the productivity and lower the production cost. Meanwhile, it can make the liquid crystal display panel more suitable to the narrow frame or non frame design of display products.
Generally, the Low Temperature Poly-silicon (LTPS) semiconductor thin film transistors can be categorized into two types: one is N-type element (NMOS) which mainly conducts with the electrons, and the other is P-type element (PMOS) which mainly conducts with the holes. A general CMOS refers to a complementary element utilizing the NMOS and the PMOS together. Under circumstances of some special applications and process condition restrictions, the liquid crystal display requires selecting the PMOS only element to be the thin film transistor of the gate driving circuit. Consequently, there is a need to design the integrated gate driving circuit for the PMOS only element to improve the performance of the gate driving circuit to promote the integration of the panel and decrease the frame width of the liquid crystal display panel in advance.